The present invention relates to an electronic timepiece with a device for automatically adjusting month-end calendar dates and having a date display means such as a date dial.
Current electronic timepieces having a date display means such as a date dial require, to realize a perpetual calendar, that displayed date be read at the end of each month to compare that date with the perpetual calendar stored in the electronic circuitry.
A date reading mechanism based on an optical means is known, as disclosed, for example, in Japanese Patent Laid-Open Publication No. Hei 3-160392. According to the disclosed means, reflectors are provided on the reverse of several dates on the date dial and each reflector is detected over four consecutive dates by advancing the date dial to read the last date.
However, because reflector detection is made while the date dial is stopped, the date dial must be advanced to read the last date, thereby requiring a complicated circuit. In addition, the disclosed means require a significant amount of time to read the last date.
It is therefore an object of the present invention to provide an electronic timepiece having a device for automatically adjusting month-end calendar dates that allows quick and secure date recognition with a simple circuit.
In order to achieve the above-mentioned object, there is provided an electronic timepiece having a device for automatically adjusting month-end dates of calendar, comprising a date dial formed on a rear surface thereof with a detection pattern composed of a reflective part and a non-reflective part both corresponding to a date display formed on a front surface of the date dial; a 24-hour switch for generating a date dial drive signal every 24 hours; a photo sensor mechanism, having a light emitting part and a photo detecting part, for reading a boundary between the reflective part and the non-reflective part of the detection pattern at a time when the date dial moves; a control circuit for determining a date formed on the date dial through a perpetual calendar circuit and outputting a necessary additional date dial drive signal by receiving the date dial drive signal from the 24-hour switch, outputting the date dial drive signal, and then receiving a signal from the photo sensor mechanism; and a date dial driving mechanism for driving the date dial according to the date dial drive signal. In this timepiece, a change in the detection pattern corresponding to that date is discriminated as a digital signal, to enable the discrimination by the date concerned alone, resulting in a simplified discriminating mechanism and circuitry and shortened discrimination time.
The boundary between the reflective part and the non-reflective part of the detection pattern may be arranged radially relative to the rotational center of the date dial, easily excluding an error in the accuracy of the detection pattern.
The detection pattern may be a particular pattern corresponding to each of at least particular dates 28, 29, and 30. This facilitates the decision of the month end at a particular date in the forward rotation of the date dial and the decision for the feeding of the date dial.
The detection pattern may be formed also for ordinary dates other than the particular dates. This allows confirmation of the feeding of the date dial on the ordinary dates.
The photo sensor mechanism may be driven intermittently, contributing to power saving.
The photo sensor mechanism may perform a detecting operation by skipping a portion on the detection pattern that shows no change, contributing to power saving.
The non-reflective part of the detection pattern may be formed by printing. Therefore, the ordinary rear surface of the date dial forms a light reflecting surface by chemically treating the surface. This can simply form the detection pattern.
A Geneva mechanism may be used to stabilize the feeding of the date dial, the Geneva mechanism being arranged such that the boundary of the detection pattern comes over the photo receiving part of the photo sensor mechanism within a rotational range in which a flange part of the Geneva mechanism is unmeshed from an intermediate date gear of a date dial driving wheel and within a range in which a backlash of the intermediate date gear is relatively small. This prevents a detection error from occurring due to the backlash of the date dial caused by an impact or the like.
A light beam detecting circuit provided on the photo sensor mechanism may switch between detection resistors on the photo receiving part of the light beam detecting circuit according to a power supply voltage. This allows the secure detection after the signal level lowers. Because the detection resistor on the photo detecting side is small in size, the freedom of circuit arrangement increases.
A light-blocking member may be provided at portions except around a light path that travels from the light emitting part of the photo sensor mechanism to the photo detecting part through the rear surface of the date dial. This prevents the diffraction (going-around of a part) of the light, decreasing the noise.
The non-reflective part of the detection pattern may have diffused reflection. Consequently, the reflection amount on the non-reflective part is stabilized, in turn stabilizing the detection of the detection pattern.
In order to further achieve the above-mentioned object, there is provided an electronic timepiece having a device for automatically adjusting month-end dates of calendar comprising a power supply, a time holding device, and a date holding device, the time holding device having a quartz oscillator for generating a reference time, a dividing circuit for dividing the output of the quartz oscillator, and a time display means operating on the basis of the output of the dividing circuit, the date holding device having a date signal generator operating on the basis of an output made every day from the dividing circuit, a date dial controller operating on the basis of an output from the date signal generator circuit, a motor operating on the basis of an output from the date dial control circuit through a driving circuit, a gear train operated by the motor, a date display means operated by the gear train, a recognition circuit for recognizing a display content from the date display means, a latch circuit for holding an output from the recognition circuit, a decision circuit 1 for operating a transmission circuit to read out contents of a memory circuit if a content held in the latch circuit is in a particular state, a year counter and a month counter in which the content of the memory circuit is held through the transmission circuit, a decision circuit 2 for determining whether the particular state held in the latch circuit is the end date of a month relative to the year counter and the month counter and, if the particular state is found the end date, moving the date to day 1, which is the first day of each month, and updating the memory circuit, and a circuit for excluding no-existing dates for controlling the decision circuit 1, the decision circuit 2, and the date dial control circuit, wherein the data is read from the memory circuit only when a particular date from the date display means is detected. This novel constitution requires no date counters corresponding to the display dates and simplifies the initializing operation for a perpetual calendar operation simply by setting up the correct year and month data in the memory circuit performing the positional detection of the date display means.
Consequently, the discriminating mechanism and circuitry are simplified to achieve quick and secure date reading.
A time difference correcting device may be provided including a correcting means for entering the output signal into the date signal generator circuit in parallel with the output from the dividing circuit. This facilitates time difference correction.
A switch may be provided for determining whether the time difference correcting device is ready for operation, the data of the year counter and the month counter being transmitted to the memory circuit only when the switch is on, controlling a timing thereof through a timer. This smoothes the update operation.
The update operation may be performed only when a change is found in a calendar data state as compared with a previous state. This secures the timing with which the rewrite operation is performed.
A correcting means may be provided for rewriting the year and month data stored in the memory circuit, resulting in secure and easy correction.
A position counter may be provided which operates in synchronization with the display content of the date display means, the position counter being reset when the date display means displays a certain position, counting the number of shift dates from the point of the resetting to exclude month-end non-existing dates. This more reliably achieves automatic adjustment of dates at the end of months.